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Countdown to first cut silage

February 17, 2021

‘I’m sure you think first cut is a long way away but preparation now is essential for best results’ Michael Verner, CAFRE dairying adviser, reminds dairy farmers. Michael adds that ‘poor quality silage often results in poor animal performance. It can also have serious economic effects during the winter feeding period with additional concentrates needing to be fed. Weather and contractors often get the blame for poor quality silage but there are other reasons! Decisions and actions you take now can help you make high quality first cut silage this year’.

As with all nutrient planning, an up-to-date soil test is vital to allow the most cost-effective use of both fertilisers and manures. An up-to-date soil analysis indicates if lime is required as well as checking Phosphorous (P) and Potash (K) levels. Aim to test 25% of the farm every year meaning the whole farm is sampled every 4 years. 

Michael continues that swards should be assessed for dead grassy material ‘Hopefully you have been able to graze silage swards in late autumn, or perhaps early spring, to avoid dead material in the crop as this will greatly improve silage quality’.  Slurry should be applied taking into account NAP guidelines. Slurry should only be spread on low grass covers and should be applied at least six weeks before silage making to avoid contamination that leads to fermentation problems. Ground which has been trampled by stock or damaged by machinery may need to be rolled to avoid soil being brought in with harvested grass, causing contamination and high ash levels in first cut silage. This is especially important on ground which will be tedded and raked.

Timely application of nitrogen (N) fertiliser will help stimulate grass growth. This will be most effective on swards with a high proportion of perennial ryegrass. Too much N produces grass with low sugar levels and any resulting silage can have high ammonia and butyric acid levels, making it less palatable. Too little N compromises yield and protein levels can be low. Once the soil has reached 5.5 degrees at 10cm depth for 3-4 consecutive days grassland can utilise 2.5 kg N/ha/day (around 2 units of N/acre/day) under ideal weather conditions. Your application rate and date need to fit with your planned harvest date. Typically apply total nitrogen (N) at from 100 to 120 kg/ha from the combined input of inorganic fertiliser and slurry. (Allow approximately 7 kg N per 4,500 litres (1,000 gallons) undiluted cattle slurry).  For Phosphate (P) and Potash (K) recommendations, the results of a recent soil analysis showing the soil index is needed.

Michael continues ‘If you employ a contractor or even if you’re using your own equipment, everyone needs to be primed and ready for your planned cutting date. On many farms, cutting date has been a compromise between yield and quality, with an aim of less than 50% ear emergence of the sward.  However by cutting earlier, there is a significant increase in nutritional quality and this will be offset by a slight yield penalty’.

Michael summary is that ‘grass silage is the most important component of the diet for at least six months of the year on the majority of dairy farms in Northern Ireland. Decisions taken now and over the next number of weeks will have a major effect on first cut silage quality next winter. A delay in harvesting of one week from mid-May onwards typically results in a reduction in D-value of up to 3 units, resulting in a reduction in milk yield of 1.0 -1.2 litres/day’.